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b=qlfauluXXRsFwdzO38odnlUZfYgoe1CFxonN5cpywYXv/xECjHvycDgDUatmFw6ia mUBDe5ELuiqS8LGCHYzjqgY9atl9gzcJssdfaXwr1lZtfNIX+aFH9UpdxKVWr2hY6o VDLCD80ua4Jz6DivTFtnW+4o83n4pkdiuavOJlynXYAeyflZipfyz6W8Oc25vrDK06 V29Vfpbmwl5PHuDi2Rr+x1QhtvO48PuKGszUIh2E5zTCPTSEE1+2o43q4S0XKjtdNU JBHIBh4AmLL5ANN4WvPQ4ZSZLskhnZK0dslMn8n6iV2b6JEvBe14AOjuZFUh5A59jT OoRg1GK9oxOYA== Date: Tue, 2 Sep 2025 14:58:46 +0300 From: Mike Rapoport To: Pasha Tatashin Cc: Jason Gunthorpe , pratyush@kernel.org, jasonmiu@google.com, graf@amazon.com, changyuanl@google.com, dmatlack@google.com, rientjes@google.com, corbet@lwn.net, rdunlap@infradead.org, ilpo.jarvinen@linux.intel.com, kanie@linux.alibaba.com, ojeda@kernel.org, aliceryhl@google.com, masahiroy@kernel.org, akpm@linux-foundation.org, tj@kernel.org, yoann.congal@smile.fr, mmaurer@google.com, roman.gushchin@linux.dev, chenridong@huawei.com, axboe@kernel.dk, mark.rutland@arm.com, jannh@google.com, vincent.guittot@linaro.org, hannes@cmpxchg.org, dan.j.williams@intel.com, david@redhat.com, joel.granados@kernel.org, rostedt@goodmis.org, anna.schumaker@oracle.com, song@kernel.org, zhangguopeng@kylinos.cn, linux@weissschuh.net, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, gregkh@linuxfoundation.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, rafael@kernel.org, dakr@kernel.org, bartosz.golaszewski@linaro.org, cw00.choi@samsung.com, myungjoo.ham@samsung.com, yesanishhere@gmail.com, Jonathan.Cameron@huawei.com, quic_zijuhu@quicinc.com, aleksander.lobakin@intel.com, ira.weiny@intel.com, andriy.shevchenko@linux.intel.com, leon@kernel.org, lukas@wunner.de, bhelgaas@google.com, wagi@kernel.org, djeffery@redhat.com, stuart.w.hayes@gmail.com, ptyadav@amazon.de, lennart@poettering.net, brauner@kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, saeedm@nvidia.com, ajayachandra@nvidia.com, parav@nvidia.com, leonro@nvidia.com, witu@nvidia.com Subject: Re: [PATCH v3 29/30] luo: allow preserving memfd Message-ID: References: <20250807014442.3829950-1-pasha.tatashin@soleen.com> <20250807014442.3829950-30-pasha.tatashin@soleen.com> <20250826162019.GD2130239@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Stat-Signature: yxk85575txqi38sx9aupqorjgkkkruoj X-Rspam-User: X-Rspamd-Queue-Id: 6AA9740012 X-Rspamd-Server: rspam05 X-HE-Tag: 1756814352-48050 X-HE-Meta: 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 Ir9iGpxO NI/hwQ/3O7pK+4K4SlQ3neAZ0oAJtdzmow8ARhysjIi1fT3mr/ZB/qNQO7o/WK+t0FJEVi6Xq9cYcjrR/GCi5WDZRR1idCREauRiH1UKNXf59kF2n9zSQg9mIk0PAwEfmiZq/OmGD0k9SQkgXg9w2RK3S/p8NumPwbJz1WScosMzyHxOrBkzcgG5GYeRrB4ORJh3l8fvpPgwxuPkYA+jCB1Z40AkRC2XinYB1dCgdZfinysfUW4nE3a/2RVgNqFWROIUhn4xp8JAtIPxmmK0BNQCIcSEI7Kk9vnVJS78qFTpezb3mGXyk8zPHvQAjFZyB+HKd0esS+rG3dhtIth+G6PbCNOEvuB/wkf2ccKIR9dl3nrZwWOUZps4eAQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 01, 2025 at 04:54:15PM +0000, Pasha Tatashin wrote: > On Mon, Sep 1, 2025 at 4:23 PM Mike Rapoport wrote: > > > > On Tue, Aug 26, 2025 at 01:20:19PM -0300, Jason Gunthorpe wrote: > > > On Thu, Aug 07, 2025 at 01:44:35AM +0000, Pasha Tatashin wrote: > > > > > > > + /* > > > > + * Most of the space should be taken by preserved folios. So take its > > > > + * size, plus a page for other properties. > > > > + */ > > > > + fdt = memfd_luo_create_fdt(PAGE_ALIGN(preserved_size) + PAGE_SIZE); > > > > + if (!fdt) { > > > > + err = -ENOMEM; > > > > + goto err_unpin; > > > > + } > > > > > > This doesn't seem to have any versioning scheme, it really should.. > > > > > > > + err = fdt_property_placeholder(fdt, "folios", preserved_size, > > > > + (void **)&preserved_folios); > > > > + if (err) { > > > > + pr_err("Failed to reserve folios property in FDT: %s\n", > > > > + fdt_strerror(err)); > > > > + err = -ENOMEM; > > > > + goto err_free_fdt; > > > > + } > > > > > > Yuk. > > > > > > This really wants some luo helper > > > > > > 'luo alloc array' > > > 'luo restore array' > > > 'luo free array' > > > > We can just add kho_{preserve,restore}_vmalloc(). I've drafted it here: > > https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/log/?h=kho/vmalloc/v1 > > The patch looks okay to me, but it doesn't support holes in vmap > areas. While that is likely acceptable for vmalloc, it could be a > problem if we want to preserve memfd with holes and using vmap > preservation as a method, which would require a different approach. > Still, this would help with preserving memfd. I can't say I understand what you mean by "holes in vmap areas". We anyway get an array of folios in memfd_pin_folios() and at that point we know exactly how many folios there is. So we can do something like preserved_folios = vmalloc_array(nr_folios, sizeof(*preserved_folios)); memfd_luo_preserve_folios(preserved_folios, folios, nr_folios); kho_preserve_vmalloc(preserved_folios, &folios_info); > However, I wonder if we should add a separate preservation library on > top of the kho and not as part of kho (or at least keep them in a > separate file from core logic). This would allow us to preserve more > advanced data structures such as this and define preservation version > control, similar to Jason's store_object/restore_object proposal. kho_preserve_vmalloc() seems quite basic and I don't think it should be separated from kho core. kho_array is already planned in a separate file :) > > Will wait for kbuild and then send proper patches. > > > > > > -- > > Sincerely yours, > > Mike. > -- Sincerely yours, Mike.